Each sport has its history and traditions - with over 100 years of history, cycling certainly has its share.
After riding with a lot of different people in various groups over the last 6 years, it finally dawned on me that no one rubs their road bike tires anymore. If you have no idea to what I am referring, then you are probably under the age of 40 or began riding less than 10 years ago. Rubbing one's tire is not the behavior of a deranged cyclist who has a fetish for his bike tires, but a habit born out of necessity in cycling years past.
When I started riding with serious riders back in the 1980s I would see everyone running a gloved hand across the surface of their tires on a regular basis - while still riding. At first, I thought they were trying to keep their hands warm with friction until I realized that they were trying to avoid flat tires. Each time there was a suspicion that the group had just ridden through broken glass on the road, you could hear gloves running over the front and then rear tire on each bike. (Note that they were alway wearing gloves - do not attempt this without gloves) Light pressure was the key, just barely touching the tire surface was enough to dislodge the glass.
Then, like now, road bike tires are made to be very light while withstanding high pressure. That meant thin casings and thin rubber due to limitations in the materials available during the period. That also meant that glass had little between its sparkling sharp edges and the inner tube that held the air. Cyclist learned that if they could knock the glass off of the tire surface before it could embed itself into the outer rubber then a flat could likely be avoided. Also, gloves were made with real leather palms and mesh backs that left a cool suntan with a characteristic oval on the back of your hand. None of this synthetic stuff you see in gloves today. The old gloves could easily withstand the friction of touching a moving tire.
I wanted to be cool like the other guys, so I started copying their rubbing behavior and proceeded to get my hand stuck between the spinning rear tire and the seat tube. This served to lock my back wheel, produce a long skid and ended with me falling over in a dead stop with my right hand stuck behind my right leg. Yep, cool as they come. Apparently there was some technique required and where you place your hand in proximity to frame and wheel is important.
Later as Aramid fibers (think Kevlar) became less expensive and more available, they were incorporated under the tread in bike tires to increase their resistance to punctures. Riders had fewer punctures and apparently the art (and necessity) of tire rubbing was no longer passed-on to beginning cyclists. Being the Luddite that I am, old habits die hard and I still rub my tires after riding through glass though I do not get my hand caught anymore. I really did not think about this ritual until I was riding with a friend last month and he asked me what I was doing - when the student is ready, the teacher appears - I could pass tradition to another rider.
He was kind and acted interested, but I could tell he did not share my enthusiasm for this behavior. Maybe some day he will understand - until then he better keep a flat repair kit handy.